Medicine

In Defense Of Rosalind Franklin. The discoverer of the structure of DNA. | by Clarisse Cornejo | Nov, 2021

here did we leave? Ah yes, at King’s College, where Franklin began to work alongside Maurice Wilkins, despite their many misunderstandings.

The two of them did not get along, there was a lot of friction between their personalities which made the two of them work separately.

She was a strong-willed, vigorous woman who liked to discuss — and it did not help at all that Wilkins first thought of her as his “assistant” and treated her as such because of her gender.

So that was the implicit arrangement: Rosalind focused on x-ray crystallography in the lab while Wilkins passed the time at the Cavendish Laboratory in Cambridge where his friend Francis Crick was with James Watson researching every possible data on the DNA model.

As you can see, during those decades there was a race to determine the structure of DNA in the scientific community.

Many biologists, physicists, and chemists were greatly influenced by the science book “What’s life?” by Erwin Schrödinger.

Schrödinger argued that the key to understanding life itself was by understanding where was our genetic information contained and how it works — when Schrödinger published his book there was a dispute whether it was proteins or DNA that contained our genes.

Watson and Crick were on a rocky path. Their attempt to build a DNA model had been disproved by Franklin when they invited her and Wilkins to see what they had come up with.

Their model was an inside-out triple helix which was wrong because, as Rosalind pointed out, DNA was water-rich and therefore the three sugar-and-phosphate backbone had to be outside instead of at the core of the prototype they had designed.

Franklin and Wilkins went back to King’s College to continue working on x-ray crystallography. As we mentioned, in 1952 “Photograph 51” appeared but that’s not all.

Rosalind had taken two x-ray photos that pictured two out of the three forms of DNA that we know today. The first is form A which presents about 75% of humidity, and the other, the most common, is the B form whose level of water is 95%.

The DNA picture of Photograph 51 was from the form B category. As a scientist, Franklin continued to collect enough data to support her hypothesis.

X-ray diffraction patterns for the two forms of DNA. At
left, form A, at right, form B. [Forensic Genealogy]

In 1953, Wilkins handed Watson and Crick Photograph 51 and that image was exactly what they needed.

The two had constructed a model of the double helix with a hypothesis to explain how it makes copies of itself by unwinding into single strands and attaching with a complementary nucleobase — either adenine (A) pairs with thymine (T) or cytosine (C) pairs with guanine (G) — creating two double helices.

As Watson wrote in his book DNA: The Story of the Genetic Revolution…

“What got us more excited was the complementarity of the base sequences along the two chains. If you knew the sequence — the order of the bases — along one chain, you automatically knew the sequence along the other.”

Months later, a series of three papers were published on Nature about the discovery of the DNA structure. Watson and Crick’s paper was rolled out first, and their names would be taught in academia from now on.

Franklin’s work only came up as ‘supporting’ to their finding.

It’s fair to say during that time she became friends with Crick and his wife, and before she decided to move to Birkbeck College to make great findings in the structure of the poliovirus, she was on good terms with Watson.

Franklin died in 1958, at the age of 38, following a diagnosis of ovarian cancer — probably due to the radiation she exposed herself during her work on X-ray crystallography.

Rosalind Franklin in 1950. [Ruiz Healy Times]

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